Doesn't have much to do with genetics either...
My (younger!) Sis got it when she was 9, which means way before me (!) &I got it when I was like 13 or so... So it doesn't have much to do with genetics. If you're a bit skinny like I am, it makes sense, sis was a bit on the 'chubby' side & I read somewhere that weight may make a bit of difference too... (But I don't have to tell you Sis has always been jealous of my bodyweight!!) & also, my period was almost always much less painful then hers... I only very occasionally got pain or cramps or such... This may have a bit to do with nutrition too, what kind of food you eat etc.
Anyway, enjoy the time you have!!!
Uhm, just make sure you're not eg doing the anorexia thing or such, this can influence your period too (you lose it). Vegetarianism can sometimes make it irregular or make it go away too... so make sure you are eating proper & get enough nutrients etc. otherwise you might consider supplements of protein, vitamins/minerals...